Optical systems often require variable focal length to allow the field of view (FOV) or the magnification to be altered. These systems with lenses and mirrors as conventional optical elements of fixed focal length use focusing mechanisms which are complicated and consist of many moving parts such as gears, motors and sliders to image a moving object or objects with high irregular shape. These mechanical focusing mechanisms become particularly difficult to employ when dealing with microlens systems for micro-electrical mechanical systems (MEMS).
The study of variable focal length microlens has been an area of activity for many years. Variable focal length is a necessary attribute in many optical applications if the object being imaged is not in a fixed position. Several recent publications have recognized that the potential for variable microlens impact significantly the field of optical applications [1][2]. The variation of focal length can be provided by a focalizing mechanism to cause the focal plane shift. The different approaches using liquid crystal methods [3][4] and electrowetting methods [5][6] have been investigated by other researchers, but the liquid crystal lens has limited application in the microlens area and the electrowetting liquid concept lens requires a high voltage source. Both methods required electrodes, which are immersed in the electrolyte solution and cause severe optical distortion. A variable microlens system overcoming these disadvantages is needed in the art.